Semiconductor devices with dual-metal gate structures and fabrication methods thereof

Abstract

Semiconductor devices with dual-metal gate structures and fabrication methods thereof. A semiconductor substrate with a first doped region and a second doped region separated by an insulation layer is provided. A first metal gate stack is formed on the first doped region, and a second metal gate stack is formed on the second doped region. A sealing layer is disposed on sidewalls of the first gate stack and the second gate stack. The first metal gate stack comprises an interfacial layer, a high-k dielectric layer on the interfacial layer, a first metal layer on the high-k dielectric layer, a metal insertion layer on the first metal layer, a second metal layer on the metal insertion layer, and a polysilicon layer on the second metal layer. The second metal gate stack comprises an interfacial layer, a high-k dielectric layer on the interfacial layer, a second metal layer on the high-k dielectric layer, and a polysilicon layer on the second metal layer.

1. A method for fabricating a CMOS device with dual-metal gate structures, comprising:
 providing a semiconductor substrate with a first doped region and a second doped region separated by an insulation layer; 
 forming an interfacial layer on the semiconductor substrate; 
 forming a high-k dielectric layer on the interfacial layer; 
 forming a first metal layer on the high-k dielectric layer; 
 forming a metal insertion layer on the first metal layer, wherein the first metal layer and the metal insertion layer are separately formed in different chambers sharing the same transfer chamber without breaking the vacuum; 
 patterning the metal insertion layer, the first metal layer, the high-k dielectric layer, and the interfacial layer exposing the second doped region of the semiconductor substrate; 
 conformably forming a second metal layer on the metal insertion layer and the second doped region of the semiconductor substrate; 
 forming a polysilicon layer on the second metal layer; 
 patterning a first metal gate stack and a second metal gate stack on the first and the second doped regions of the semiconductor substrate; and 
 forming a sealing layer on sidewalls of the first gate stack and the second gate stack. 
 
     
     
       2. The method according to  claim 1 , wherein the interfacial layer is formed resulting from wafer cleaning processes, or wherein the interfacial layer is formed by thermal or chemical oxidation. 
     
     
       3. The method according to  claim 1 , wherein the high-k dielectric layer is formed by atomic layered deposition (ALD), chemical vapor deposition (CVD), or physical vapor deposition (PVD). 
     
     
       4. The method according to  claim 3 , wherein a silicon atomic ratio and a dielectric constant of the high-k dielectric layer are adjusted during ALD, CVD, and PVD. 
     
     
       5. The method according to  claim 3 , wherein adjusting an Hf and a Si precursor cycle numbers during a nano-laminated ALD forms the high-k dielectric layer comprising a HfSiO x  with 30-80% silicon atomic ratio and 7-20 dielectric constant. 
     
     
       6. The method according to  claim 1 , further comprising a nitrification process during or after the formation of the high-k dielectric layer. 
     
     
       7. The method according to  claim 6 , wherein the high-k dielectric layer is nitrified by thermal or plasma nitrification. 
     
     
       8. The method according to  claim 1 , wherein the first metal layer and the second metal layer are separately formed by ALD or PVD. 
     
     
       9. The method according to  claim 1 , wherein the second metal layer is formed after removal of the first metal layer from the second doped region. 
     
     
       10. The method according to  claim 1 , wherein the first metal gate stack comprises a tri-layer metal structure comprising the first metal layer, the metal insertion layer, and the second metal layer, and wherein the second metal gate stack comprises a mono-layer metal structure comprising the second metal layer. 
     
     
       11. The method according to  claim 1 , wherein the metal insertion layer is directly formed by ALD or PVD after formation of the first metal layer. 
     
     
       12. The method according to  claim 1  wherein the step of patterning a first metal gate stack and a second metal gate stack comprises removal of the first metal layer and the second metal layer by dry etching, wet etching, or combination thereof. 
     
     
       13. The method according to  claim 12  wherein the insertion metal layer serves as protection of the first metal layer from patterning the first metal gate stack and the second metal gate stack. 
     
     
       14. The method according to  claim 1 , wherein the polysilicon layer is formed by chemical vapor deposition. 
     
     
       15. The method according to  claim 1 , wherein the sealing layer is formed by CVD or ALD. 
     
     
       16. The method according to  claim 1 , wherein the sealing layer is etched by an anisotropic etching process remaining on sidewalls of the first gate stack and the second gate stack.